OneMoreTime
New Member
Posts:7
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| 05 Sep 2011 10:45 AM |
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My wife and I are looking to build one more house. Sometimes she calls me crazy because she knows I'll do a lot of the work myself to save money. I'm not so sure about doing ICF myself though due to no experience. However I'm still leaning heavily towards it due to the energy efficieny gains and the strength of the house in tornado alley.
I searched the topic of geothermal in this forum and found varying feedback. Thoughts tended to be heavily driven by factors such as climate and cost. I'm looking to build the house in the next 24 months and am strongly leaning towards an ICF/geothermal set up. One key callout in contrast to the other threads I've read is that I am maybe in a more extreme climate. I would greatly appreciate anyone's thoughts considering the following circumstances:
-1 1/2 story house on a hill in the country in western Iowa
-2,300 sq. ft. on the main with full basement (walk-out facing west)
-800 sq. ft. on the second floor
-Summers here typically see 1-2 weeks in the mid to high 90s and 4-6 weeks in the 80s
-Winters here typically see 1-2 weeks of lows in the sub-zero range (bottomed out at -20 in 2010) and 3-4 weeks of lows in the 0-teens range
One thing I didn't see mentioned in the other geothermal threads is the federal tax credit of 30% with no cap set to expire in 2016. Given this, do you feel that added cost for geothermal is on a more level playing field? Also, does anyone know what the typical efficiency gains of a geothermal equate to in the tonnage rating on an HVAC unit? For example, if a stick frame version calls for a 5 ton air-to-air, would you not skip a beat with a 4 ton geo?
We have an air-to-air heat pump now on a 2,400 sq. ft. stick frame ranch (2x6 exterior walls, no walk-out) and our highest elec bill for heating in the last 12 months was $238 (seperate meter for heat pump, water heaters, and a garage heater kept at 45 degrees). Highest cooling was around $104. I'm hoping to cut that in half. Is this realistic?
Thanks in advance,
Ryan |
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ICFHybrid
Veteran Member
Posts:3039
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| 06 Sep 2011 05:18 PM |
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For example, if a stick frame version calls for a 5 ton air-to-air, would you not skip a beat with a 4 ton geo? 5 tons of heating or cooling is supposed to be the same, whatever the source. Where you will see an improvement is with the performance of a geothermal heat pump over your older air to air unit. It will convert electricity to heating and cooling much more "efficiently" than your old air source unit, whatever it is. And, of course you will do better on the insulation and air leakage in your new home through the construction methods. What are the performance ratings stamped on your existing heat pump? SEER? HSPF? What is the insulation in your existing home, particular the ceilings and basement? Are the walls insulated with standard fiberglass batts? Not clear on your home sizing; Current home: 2400 sf ranch, all main floor, no basement? Slab? Crawlspace? New home planned: 2300 sf, evenly split between main and basement PLUS 800 sf second floor for a total of 3100 sf? |
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OneMoreTime
New Member
Posts:7
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| 06 Sep 2011 11:08 PM |
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ICFHybrid,
My current house is 10 years old. I couldn't find a SEER rating on the unit but the documentation says "up to 13.2". It's a Lennox HP26-048-11P. My current insulation is R-19 fiberglass batts in 2x6 walls. The attic has ~12" of blow in cellulose. The basement has R-13 fiberglass batts in 2x4 walls. The foundation is 9' poured walls with no walk out. There are 4, 4'x5' windows though. There is no insulation in the ceiling between the basement and main floor.
Current home size is 2,400 sq. ft. on the main floor with a 2,400 sq.ft basement for a total of 4,800 sq. ft. The new home will be around 2,300 on the main plus 2,300 in the basement, plus 800 on the second for a total of 5,400 sq. ft. Hope this helps. Please let me know if there is any other information you would find helpful
Thanks,
Ryan
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ICFHybrid
Veteran Member
Posts:3039
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| 07 Sep 2011 01:04 AM |
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I'm hoping to cut that in half. Is this realistic? Roughly speaking, a larger home will use more heating and cooling energy, but going to the ICF construction will get you some wall and basement insulation 50% - 100% better and the geo unit might deliver up to 50%-75% better than the heat pump you have. Cutting your heating costs in half with ICF and geothermal is probably doable, but once you have the design and construction, you will need to have a heating and cooling load calculation "Manual J" done to properly size your heating unit and get a better idea of what the heating and cooling costs will be. |
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OneMoreTime
New Member
Posts:7
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| 07 Sep 2011 07:48 AM |
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So the long and the short of it... The efficiency benefit of the geothermal outweighs the upfront expense even in an ICF in this climate? |
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ICFHybrid
Veteran Member
Posts:3039
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| 07 Sep 2011 10:16 AM |
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I think cutting your heating bill in half is achievable. It's up to you to decide if that will justify the upfront costs. I would recommend that you contract with a specialist to do a heating and cooling load analysis on the design in order to get a more precise determination of the costs and benefits of above-code insulation and a more efficient heating plant. It will be money well-spent to have the information. Do not rely on contractors for the Manual J who are trying to sell you something, be it insulation or the geothermal. Make sure you get multiple bids. even in an ICF The efficiencies go hand in hand. Having a more efficient building shell helps you save money not only on the energy, but in sizing the heating and cooling unit in the first place. What's harder to put a value on is the quietness of an ICF home, not to mention the added security from tornadoes. |
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jonr
Senior Member
Posts:5341
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| 07 Sep 2011 12:20 PM |
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Exactly. |
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OneMoreTime
New Member
Posts:7
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| 08 Sep 2011 06:06 PM |
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Thank you for the feedback. I'll be sure to have an expert with ICF experience size/design the system. I don't know that ICF is very popular around here yet and hence am not sure how many HVAC folks have experience designing systems for them. |
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ICFHybrid
Veteran Member
Posts:3039
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| 08 Sep 2011 08:15 PM |
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I don't know that ICF is very popular around here yet and hence am not sure how many HVAC folks have experience designing systems for them. That is the same problem I ran into. If it isn't used much in your area, you can count on hearing lots of ignorance about it. Everybody and their brother will try and turn you to something they are familiar with and can sell you. |
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BrucePolycrete
Advanced Member
Posts:524
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| 08 Sep 2011 09:29 PM |
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Most HVAC suppliers use software to size the units, and most standard software offers ICF as a building envelope choice (input). It should be no big deal. |
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OneMoreTime
New Member
Posts:7
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| 08 Sep 2011 10:40 PM |
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That's good to know. I'll be sure to ask when the sizing begins to ensure they have software that can account for ICF walls. |
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dmaceld
Veteran Member
Posts:1465
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| 08 Sep 2011 11:18 PM |
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Posted By OneMoreTime on 08 Sep 2011 06:06 PM
Thank you for the feedback. I'll be sure to have an expert with ICF experience size/design the system. I don't know that ICF is very popular around here yet and hence am not sure how many HVAC folks have experience designing systems for them.
I agree with Bruce. Specific ICF experience is secondary to competence with the use of an HVAC sizing program like Wrightsoft. It has an ICF option built into the program. One big benefit of using an HVAC contractor who is open minded and experienced with using a good s/w program is you can get a good picture of how the heat load varies from room to room. The heating/cooling requirement for a south facing room with exposed windows will vary a lot from that of a north facing room with minimal glazing. This directly impacts duct sizes and register placements. |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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ICFHybrid
Veteran Member
Posts:3039
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| 08 Sep 2011 11:37 PM |
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I think it is well worth it to pay a fee to get an independent heating and cooling study done by a pro who does not and cannot sell you something based on the results. That would specifically exclude traditional HVAC contractors. |
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jeepster
Basic Member
Posts:153
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| 09 Sep 2011 01:32 AM |
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I recently questioned my HVAC contractor about the geo thermal that they've spec'd out for my house. I told him that many systems are oversized in ICF houses, because the conventional calculations don't take into account how tight the ICF house is. He said that their program has ICF as an option for walls and that they had to pay big money for that program (50k). He said they went with that software simply because it had options, like ICF, that aren't typically included in many software packages. I don't know if he's feeding me a line of crap, but I've got no reason to doubt him.
I'm getting a waterfurnace envision with a dual capacity compressor, so it can act like a smaller system until demand increases. Also, regarding the coolant pumps, the envision has a mode where the pump spins slowly when the system is not needed. This apparently draws a low amount of current, and it takes less current to get it up to speed.
I've got high hope for this system. I mentioned to him that it seems like a lot of people complain about the synergy system regarding their electric bill. He said that they don't install those anymore. He didn't go into details, but I had a feeling they just aren't as efficient.
On a side note, I'd have to beleive that radiant floor heat would have to be grossly in-efficient, since the potential for loosing the heat to the earth is so great. I can understand radiant if you can take advantage of a wood burning boiler or solar, since that could be considered free fuel. Wouldn't be more efficient to simply heat the air and then seal your house so well that the air cannot escape very easy? |
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BrucePolycrete
Advanced Member
Posts:524
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| 09 Sep 2011 06:09 AM |
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Wood's not free, unless cutting and splitting firewood is your hobby of choice. Radiant floor heat is wonderful. Study thermal mass benefits to understand better. Be sure to insulate under the slab. |
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dmaceld
Veteran Member
Posts:1465
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| 09 Sep 2011 12:04 PM |
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Posted By jeepster on 09 Sep 2011 01:32 AM
He said that their program has ICF as an option for walls and that they had to pay big money for that program (50k). He said they went with that software simply because it had options, like ICF, that aren't typically included in many software packages. I don't know if he's feeding me a line of crap, but I've got no reason to doubt him.
On a side note, I'd have to beleive that radiant floor heat would have to be grossly in-efficient, since the potential for loosing the heat to the earth is so great. I can understand radiant if you can take advantage of a wood burning boiler or solar, since that could be considered free fuel. Wouldn't be more efficient to simply heat the air and then seal your house so well that the air cannot escape very easy?
50k sounds like an exaggeration, but the rest of what he says is pretty much right on. My HVAC nephew-in-law has Wrightsoft. It is something on the order of 8 to 10k to buy with s/w maintenance included. But 50k may be right if he buys every option for the program, particularly if he does big time commercial HVAC. Take some time to peruse the radiant forum here. You'll find a few key points such as radiant doesn't heat you by heating the air and under slab insulation is a very important part of the design. Also wood isn't 'free.' In fact it can cost more than resistance electric heating. Now solar is, except of course for the capital investment to capture it. Radiant can be more efficient than a warm air system if done correctly. |
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Dana1
Senior Member
Posts:6991
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| 09 Sep 2011 12:26 PM |
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The existing house is 10 years old, already has basement insulation, so the U-values between that and a minimalist ICF won't be 2x, maybe not even 1.5x unless those batts are completely mis-installed and the place leaks like a sieve (which it might, but I wouldn't assume that.) ICF makes it easy to air-seal, but without detailing it correctly at all windows doors and at the ceiling, tightness is by no means guaranteed. (The more idiot-proof you make a system, the more creative the idiots seem to become. :-) )
It could easily be that the largest difference heat load between where you are now and a new house will be related to window size & type- leaky double-hungs suck just as badly in an ICF building as in stick built, and added glass area isn't easily made up for by ever-higher R walls.
The difference in whole-system COP between your air-source vs. a geo system depends a bit on climate & location. A 2/1 situation would be somewhat rare, but 1.5/1 pretty common. In some climates and with an optimal floor plans, continously variable speed ductless air-source can equal or exceed geo on seasonal performance.
Bottom line, can you cut your heating costs in half?
Sure! But getting there will require actually designing it. It's not merely a function of ICF vs. stick-built or geo vs. air-source. It's never that simple. |
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OneMoreTime
New Member
Posts:7
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| 09 Sep 2011 11:39 PM |
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More good info! Thanks everyone. In an effort to fill in any gaps... The current windows are all double pane casement with low-e coating and argon. I'm planning something similar for the next house. Certainly open to suggestions though. When they first installed my "big window" (12 windows covering about an 8 x 13 foot space), they did not assemble it correctly and used glass with no low-e and no argon. The first Thanksgiving had 26 people here and there was snow on the ground but a super sunny day (no blinds yet either). It was 80 degrees in the house and the heat was not running. Had to open some windows just to cool things down. The manufacturer did stand by their product and replaced the panes. I'm definitely a fan of low-e and argon but that was something pushed on me over 10 years ago. I'd be certainly open to something better if the cost/benefit was there. My goal is to have an extremely energy efficient home so that when I'm old I can afford the electric bill.  |
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